A press is used to bend a metal sheet during the manufacture of pipe or tubing from the metal sheet. This metal sheet extends in a longitudinal plane and is bent at least one longitudinal edge, to which end the bending press has at least one two-part bender that is connected to at least one actuator, and a force acting between the two parts of the bender and generated by the actuator is transmitted through at least one tie rod.
In the fabrication of welded pipes, in particular, of large-diameter pipe, a tubular body is formed in a first step from a sheet plate. In a second step, this body is then welded at the resulting seam of the longitudinal edges of the sheet that are pressed together. In the first process step, the longitudinal edges of the sheet are bent, normally upward. Bending presses for this purpose are well-known.
In a known embodiment, two separate individual presses are employed to bend the two longitudinal edges of the metal sheet. This solution is disadvantageous in that the considerable bending forces laterally shift the workpiece.
In an alternative second embodiment, an approach is thus also known whereby the bending devices for the two edges of the sheet are in one machine, thereby enabling any relative shifting between the two bending devices to be prevented. Accordingly, a fixed frame structure is provided in which the two bending devices are fixed. This approach has disadvantages, however, when the sheet width change. Specifically, in order to adjust the machine to a desired predefined sheet width, the tools are displaced to the required position, i.e., in the case of narrow sheet widths the tools are displaced toward the center of the press. However, it is there that the deformation of the framework-shaped machine is the greatest, with the result that for narrow sheets the deformation is not insignificant in response to the forces exerted by the tools.